@article{10_4171_ggd_130,
     author = {Kai-Uwe Bux and Mikhail Ershov and Andrei S. Rapinchuk},
     title = {The congruence subgroup property for {Aut }$F_2$:  {A} group-theoretic proof of {Asada{\textquoteright}s} theorem},
     journal = {Groups, geometry, and dynamics},
     pages = {327--353},
     year = {2011},
     volume = {5},
     number = {2},
     doi = {10.4171/ggd/130},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ggd/130/}
}